With the widespread application of a metallic shell of a mobile phone, the requirement on the appearance of the shell is improved increasingly, and integrity of the appearance of the shell is preferred by more people. However, most of the current mobile phones are limited by the communication function or limited by the processing technology, resulting in the existences of both a metallic portion and a non-metallic portion in the shell. The non-metallic portion is made of a material different from that of the metallic portion, and thus exhibits a different colour from the metallic portion, resulting in a less preferred integral appearance of the shell of the mobile phone and an unsatisfied user experience.